JP2010145674A - Image display device and head mount display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display device and a head mount display, observing an external field brightly while satisfactorily improving visibility of an image. <P>SOLUTION: External light of the specified wavelength range which contains the same wavelength range as that of the image light made incident to an optical pupil is dimmed by means of a dimming shutter. Hence, light components of the same system color as the image light made incident to the optical pupil are dimmed from the external light, and the observed external field is colored with colors different from a display image to produce a hue difference between the display image and the external field. Based on the hue difference in addition to a luminance difference produced by dimming the external light, the visibility of the display image is then satisfactorily improved. The external light is dimmed only in the specified wavelength range in the visible light region by means of the dimming shutter and, an observer can observe the external field overwhelmingly brightly via the dimming shutter and an optical path combiner as compared with the case where the transmittance over the whole range of visible light region is reduced. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention uses an optical element having reflection / transmission characteristics as an optical path combiner, and an image observation apparatus capable of observing a display image of the display element and the outside simultaneously, and a head mounted display (hereinafter referred to as a head mounted display) including the image display apparatus. , Also referred to as HMD).

  Using a film with reflection and transmission characteristics formed on a transparent substrate, the image light from the display element is reflected in the direction of the observer's pupil, and at the same time the external light is transmitted, and the image (virtual image) and the external environment are superimposed. Devices known as HUD (Head Up Display) and HMD are well known as devices for visual recognition. By using a see-through device that can observe the image and the outside world at the same time, it is possible to additionally observe the necessary information displayed without diverting the line of sight from the outside world in front of various scenes. Is very useful.

  However, in a see-through device, it is difficult to observe a display image when the outside is bright, and thus some device for improving the visibility of the image is required. In order to improve the visibility of the image, there is a method of providing a white (without color filter) liquid crystal shutter on the outside side of the eyepiece optical system and increasing the visibility of the image by reducing the transmittance of outside light with the liquid crystal. It is common. For example, Patent Document 1 proposes a video display device using TN liquid crystal or STN liquid crystal as a light-shielding shutter. In this video display device, the transmittance can be uniformly changed over the entire visible light region, and the visibility of the video is improved by uniformly reducing the transmittance over the entire visible light wavelength region.

  On the other hand, there is a report that a high-contrast image can be obtained by using a combiner having wavelength selectivity and angle selectivity. For example, Patent Document 2 proposes a see-through video display device using a cholesteric liquid crystal as a combiner. Cholesteric liquid crystal has wavelength selectivity and angle selectivity, and reflects light in a narrow band limited to a specific incident angle. Accordingly, external light having the same wavelength as the image light reflected by the combiner is reflected (dimmed) outward by the combiner, so that a high-contrast image can be obtained.

Japanese Patent No. 3354008 Japanese Patent No. 2564366

  However, in the configuration of Patent Document 1, in order to improve the visibility of an image, the transmittance is uniformly reduced over the entire wavelength region of visible light, so the outside world observed through see-through becomes very dark.

  Further, as described in Patent Document 2, in order to improve the visibility of an image, only by using a combiner having wavelength selectivity and angle selectivity, considering the size of the optical pupil on which the image light is incident, External light of the same wavelength also enters the optical pupil and is not sufficient to improve the visibility of the image light. Hereinafter, this point will be further described.

  In the configuration of Patent Document 2, the theory that “the external light having the same wavelength as the image light reflected by the combiner is reflected to the outside by the combiner so that a high-contrast image can be obtained” is the size of the optical pupil. Is valid only when it is assumed that there is only one point (ie, the size of the optical pupil is almost zero). In practice, the optical pupil has a size, and all light incident on the pupil diameter must be taken into account.

  For example, as shown in FIG. 10, when the size of the optical pupil E is taken into consideration, both the external light toward the pupil center and the external light toward the pupil end are incident on the combiner 101 at substantially the same angle. On the other hand, since the combiner 101 is disposed close to the optical pupil E, the reflection angle on the combiner 101 differs between the image light incident on the pupil center and the image light incident on the pupil end. Since the combiner 101 has wavelength selectivity and angle selectivity, the image light wavelength incident on the optical pupil E differs depending on the reflection angle. That is, since image light having a reflection angle on the combiner 101 different from that of the external light is also incident on the optical pupil E, the external light having the same wavelength as all the image light wavelengths incident on the optical pupil E is blocked by the combiner 101. (The wavelength band of the image light incident on the optical pupil E is wider than the wavelength band of the external light blocked by the inner combiner 101 of the external light incident on the optical pupil E). Therefore, using only the combiner 101 is not sufficient to improve the visibility of the image light.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a video display device capable of brightly observing the outside world while sufficiently improving the visibility of the video, and the video. To provide an HMD including a display device.

  An image display apparatus of the present invention includes a display element that displays an image, and an optical path combiner that reflects image light from the display element and guides it to the optical pupil, and transmits external light to the optical pupil, An image display device for observing the outside world in a see-through manner together with a display image at the position of the pupil, the dimming means disposed on the side opposite to the optical pupil with respect to the optical path combiner and reducing the transmittance of the outside light The dimming means further comprises a transmittance in a specific wavelength region including the same wavelength region as the image light incident on the optical pupil in the visible light region, which is lower than the transmittance in a wavelength region other than the specific wavelength region. It is characterized by that.

The video display device of the present invention, the wavelength width as the intermediate value of the transmittance of the external light is the maximum value and the minimum value in the dimming means and W _1, the maximum intensity of the image light entering the optical pupil half wavelength When the width W _2,
W ₂ <W ₁ ≦ 100 nm
It is desirable that

In the video display device of the present invention, the optical path combiner is a volume phase type reflection type hologram optical element, and a diffraction reflection wavelength range of the hologram optical element is included in the specific wavelength range, and the hologram optical If the half-value wavelength width of the diffraction efficiency of the element is W ₃ ,
3W ₃ ≦ W ₁
It is desirable that

  In the video display device of the present invention, it is desirable that the specific wavelength range is any one of red, green, and blue.

  In the video display device of the present invention, the dimming means may have a saturation of transmitted light of 10 or more (in the LCh color system) when light from a C light source that is one of the standard light sources is incident. desirable.

In the video display device of the present invention, when the hue angle difference in the LCh color system between the external light incident on the optical pupil and the video light incident on the optical pupil is Δh,
45 ° ≦ Δh ≦ 315 °
It is desirable that

In the video display device of the present invention,
135 ° ≦ Δh ≦ 225 °
It is further desirable that

  In the video display device of the present invention, it is desirable that the transmittance in the specific wavelength range in the dimming means is variable.

  In the video display device of the present invention, the dimming means may be a liquid crystal element using guest-host liquid crystal.

  In the video display device of the present invention, the dimming means may be a liquid crystal element using chiral nematic liquid crystal.

  In the video display device of the present invention, a plurality of the dimming means may be provided so as to be selectively usable, and the specific wavelength ranges of the dimming means may be different from each other.

  The image display apparatus of the present invention further includes an optical member that guides the image light from the display element by totally reflecting the light inside, and the optical path combiner is a volume phase type reflection type hologram optical element. In addition, the hologram optical element may be configured such that image light from the display element guided through the optical member is diffracted and reflected and guided to the optical pupil.

  In the image display device of the present invention, the hologram optical element has an axially asymmetric positive optical power and constitutes at least a part of an eyepiece optical system that guides image light from the display element to an optical pupil. May be.

  The HMD of the present invention includes the above-described video display device of the present invention and support means for supporting the video display device in front of an observer's eyes.

  According to the present invention, the external light in a specific wavelength region including the same wavelength region as the image light incident on the optical pupil is attenuated (the transmittance is reduced) by the dimming means. As a result, the light component having the same color as the image light incident on the optical pupil is attenuated from the external light, so that the observed external environment (background) is colored in a different color from the display image (virtual image). A hue difference occurs with the outside world. Therefore, in addition to the luminance difference due to the attenuation of external light, the above-described hue difference can sufficiently improve the visibility of the display image. For example, a liquid crystal shutter or a color filter that reduces the transmittance only in a specific wavelength region in the visible light region can be used as the dimming unit.

  In addition, since the specific wavelength range (including the wavelength range of the image light) that is the attenuation wavelength range of the external light is wider than the wavelength range of the image light incident on the optical pupil, for example, the optical pupil is a certain size. Even if the main wavelength of the image light (the wavelength with the highest intensity) fluctuates for each incident position of the image light in the optical pupil, the light component of the same color as the image light is reduced from the external light. Can be light. Therefore, the visibility of the display image can be sufficiently improved regardless of the position of the observer's pupil in the plane of the optical pupil having a certain size.

  Moreover, since the external light is attenuated only in a specific wavelength region in the visible light region by the dimming means (because the external light is not attenuated over the entire visible light region), the transmittance of the entire visible light region in the past can be increased. Compared with the case where the dimming means for reducing is used, the observer can observe the outside world overwhelmingly brightly through the dimming means and the optical path combiner.

  An embodiment of the present invention will be described below with reference to the drawings. First, the point of the video display device of the present invention will be described, and then a specific example in which this is applied to the HMD will be described.

(1. About video display device)
FIG. 1 is an explanatory view schematically showing a configuration of a video display device 1 of the present invention. The video display device 1 includes a display element 2, an optical path combiner 3, and a dimming shutter 4.

  The display element 2 is a light modulation element that displays an image by modulating light from a light source (not shown) based on image data, and is composed of, for example, a transmissive liquid crystal display element. In this embodiment, the image light emitted from the display element 2 is monochromatic light. Therefore, when the image light is, for example, green (G) color light, the display element 2 may be illuminated using an LED that emits G light as a light source, or the display element 2 having a G color filter may be used. It is good also as a structure illuminated with white light.

  The dimming shutter 4 is a dimming unit that is disposed on the side opposite to the optical pupil E with respect to the optical path combiner 3 and reduces the transmittance of external light. The details will be described later. As the light-reducing shutter 4, a member that absorbs or reflects light in a specific wavelength range (for example, including the G image light wavelength range) described later can be used. For example, a color filter that absorbs predetermined color light, which will be described later. A guest host liquid crystal or a liquid crystal element using chiral nematic liquid crystal can be employed.

  The optical path combiner 3 is an optical member that reflects video light from the display element 2 and guides it to the optical pupil E, and transmits external light and guides it to the optical pupil E. Therefore, the observer can observe the virtual image of the display image through the optical path combiner 3 at the position of the optical pupil E, and at the same time can observe the outside world through the dimming shutter 4 and the optical path combiner 3 in a see-through manner. .

  The optical path combiner 3 only needs to have both functions of reflection and transmission. For example, the optical path combiner 3 can be composed of a half mirror, a reflection hologram (HOE) in which interference fringes are recorded in layers, a multilayer film, and the like. In particular, it is desirable to use a wavelength selective combiner that can reflect only light in an arbitrary wavelength region, such as a reflective HOE or a multilayer film. By matching the reflection wavelength with the image light wavelength, the image light can be observed brightly, and external light other than the reflection wavelength can be transmitted, so that the external light can also be observed brightly.

  In particular, it is possible to easily produce an optical path combiner 3 having a narrow reflection wavelength region by using a volume phase type reflection type HOE. Volume phase type reflection type HOEs are manufactured by interference exposure with coherent light. Depending on the refractive index difference (Δnd) of materials used, manufacturing conditions (exposure amount, post-exposure processing (temperature)), etc. The reflection wavelength range can be arbitrarily controlled. Holographic photosensitive materials for producing HOE used for such applications include photopolymers, silver salt materials, dichromated gelatin, and the like, among which photopolymers that can be manufactured by a dry process are desirable.

(2. About dimming shutter)
Next, details of the dimming shutter 4 will be described.

<About the wavelength characteristics of the dimming shutter>
2A is an explanatory view showing the wavelength characteristic of the transmittance of the light reducing shutter 4, FIG. 2B is an explanatory view showing the wavelength characteristic of the external light, and FIG. It is explanatory drawing which shows the wavelength characteristic of the image light which injects into the optical pupil E, and external light. In addition, the light intensity of the vertical axis | shaft of FIG.2 (b) (c) is normalized with the maximum intensity | strength.

The dimming shutter 4 reduces the transmittance of external light in a specific wavelength region including the same wavelength region as the image light incident on the optical pupil E in the visible light region, compared to the transmittance in a wavelength region other than the specific wavelength region. Let For example, the image light reflected by the optical path combiner 3 and reaching the optical pupil E is G monochromatic light, the peak wavelength of the image light (the wavelength at which the light intensity reaches a peak) is 520 nm, and the half width of the image light is 15 nm. In this case, the dimming shutter 4 lowers the transmittance of external light in the band of 480 to 560 nm as the specific wavelength region, compared to the transmittance in the wavelength region other than the specific wavelength region. The wavelength width of the specific wavelength band refers to the wavelength width W ₁ (nm) in FIG. 2 (a). The wavelength width W ₁ is an intermediate value between the maximum value and the minimum value when the maximum value of the transmittance of external light in the light reducing shutter 4 is a (%) and the minimum value is b (%). The wavelength width when ((a + b) / 2). Further, the half-value width of 15 nm of the image light indicates the half-value wavelength width W ₂ (nm) of the maximum intensity of the image light incident on the optical pupil E in FIG. Thereby, the following effects can be obtained.

  For example, in a configuration in which an ND filter, a TN liquid crystal, an STN liquid crystal, or the like is used as a dimming shutter for external light, and the transmittance of the external light is uniformly reduced over the entire wavelength region of visible light, Even if the visibility of the image can be improved by the “difference”, the external environment is observed very darkly in order to reduce the transmittance of the external light over the entire wavelength region of visible light.

  On the other hand, as in the present invention, by reducing only the external light in a specific wavelength range (a wavelength range of 480 to 560 nm in the above example) in the visible light region by the light reducing shutter 4, Compared with a configuration in which the transmittance of external light is lowered over the entire wavelength range of visible light, the degree of darkening of the external environment can be reduced, and the observer overwhelms the external environment via the dimming shutter 4 and the optical path combiner 3. It can be observed brightly.

  Further, the dimming shutter 4 is observed because the ratio of the light component of the same color as the image light in the external light is reduced by reducing the external light in a specific wavelength region including the same region as the image light wavelength. The outside world is colored in a color different from the image (purple in the above example), and the visibility of the image is improved by the hue difference. That is, according to the present invention, it is possible to sufficiently improve the visibility of an image by using “hue difference” in addition to “luminance difference” between external light and image light. Details of the “hue difference” will be described later.

  In addition, the light attenuation wavelength range (specific wavelength range) of the external light is wider than the wavelength range of the image light incident on the optical pupil E, including the wavelength range of the image light. Even when the main wavelength (wavelength having the highest intensity) of the image light varies for each incident position of the image light in the optical pupil E, the light component having the same color as the image light can be reduced from the external light. Therefore, the visibility of the display image can be sufficiently improved regardless of the position of the observer's pupil in the plane of the optical pupil E having a certain size.

  In addition, since the visibility of the image can be improved by the “hue difference”, the transmittance in the light shielding wavelength region (specific wavelength region) is reduced compared to the case where the visibility of the image is improved only by the “brightness difference”. Even if the degree is small (for example, even if the transmittance of the light shielding region is 30%), the visibility of the video can be sufficiently improved.

Further, the wavelength width W ₁ of the specific wavelength region in the light reducing shutter 4 is wider than the half-value wavelength width W ₂ of the image light in order to surely reduce the light component of the same color as the image light from the outside light. Is desirable. Further, it is desirable that the wavelength width W ₁ has an upper limit of about 100 nm so that the observed outside world does not become too dark. In the above example, W ₂ = 15 nm and W ₁ = 560-480 = 80 nm, satisfying the above conditions.

In other words, if W ₂ <W ₁ is satisfied, the light component of the same color as the image light can be surely attenuated from the ambient light, and if W ₁ ≦ 100 nm is satisfied, the wavelength range where the transmittance is reduced can be reduced. Since it is limited, it can be avoided that the outside world is observed darkly. From this, it can be said that it is desirable to satisfy the following conditional expression. That is,
W ₂ <W ₁ ≦ 100 nm
It is.

By the way, when the optical path combiner 3 described above is composed of a volume phase type reflection type HOE, the diffraction reflection wavelength range of the HOE is included in the specific wavelength range, and the half-value wavelength width of the diffraction efficiency of the HOE is reduced. If W ₃ is W ₁ and the wavelength width of the specific wavelength region where the light reducing shutter 4 is dimmed is W ₁ ,
3W ₃ ≦ W ₁
It is desirable to satisfy The reason is as follows.

  Since the optical path combiner 3 made of HOE has wavelength selectivity and angle selectivity, when the reflection angle on the optical path combiner 3 is different, the reflection wavelength of the image light is also different. That is, the peak wavelength of the diffraction efficiency in the HOE is different for each of the video light incident on each position in the plane of the optical pupil E.

  Here, FIG. 3A is an explanatory diagram schematically showing the optical path of the image light that is diffracted and reflected by the optical path combiner 3 and is incident on the center and upper and lower ends of the optical pupil E, and FIG. It is explanatory drawing which shows the wavelength characteristic of the diffraction efficiency of HOE which comprises the optical path combiner 3. FIG. As shown in FIG. 3A, in consideration of the size of the optical pupil E, the optical path combiner 3 is arranged close to the optical pupil E. The reflection angles to the lower end are different, and the main wavelengths of the reflected image light are different.

For example, it is assumed that the diffraction peak wavelength of HOE is 520 nm and the half-value wavelength width W _{3 of} diffraction efficiency is 15 nm. The HOE reflects light incident at an incident angle of 30 ° toward the pupil center at a reflection angle of 30 °. If the distance between the optical path combiner 3 and the optical pupil E is 14 mm and the pupil size in the vertical direction is 2.5 mm, the reflection direction to the upper end of the pupil and the lower end of the pupil is shifted by about 5 degrees with respect to the pupil center. ing. At this time, as shown in FIG. 3B, the diffraction peak wavelength is about 529 nm for the light incident on the upper end of the pupil and about 510 nm for the light incident on the lower end of the pupil, and is diffracted for the light incident on the pupil center. It differs from the peak wavelength (520 nm) by about 10 nm.

As the angle difference with the light incident on the center of the pupil increases, the wavelength shift increases, and the wavelength range of the entire image light incident on the optical pupil E becomes wider than the half-value wavelength width of the diffraction efficiency of the HOE (described above). In the example of FIG. For this reason, in order to improve the visibility of the image light, the wavelength width W ₁ of the specific wavelength region where the light reducing shutter 4 is dimmed is at least three times the half-value wavelength width W ₃ of the diffraction efficiency of the HOE. Is desirable. If W ₁ is 80 nm as described above, the above conditional expression can be easily satisfied by using HOE having W ₃ of 15 nm as the optical path combiner 3.

  That is, by satisfying the above conditional expression, the transmittance of the external light can be increased in a specific wavelength range including the same wavelength range as the entire wavelength range of the image light incident on each position of the optical pupil E having a certain size. Since it can be dropped, the visibility of the displayed image can be reliably improved regardless of the position of the observer's pupil in any position in the plane of the optical pupil E.

  In the above description, an example in which the specific wavelength region in which the light reducing shutter 4 is dimmed is the G wavelength region including the G image light wavelength region is described. However, the specific wavelength region is the red (R) image light. The wavelength range of R including the wavelength range may be used, or the wavelength range of B including the wavelength range of blue (B) video light may be used. That is, the specific wavelength range may be any of the RGB wavelength ranges. Since general image light is composed of at least one of RGB light, the dimming shutter 4 reduces external light in combination with any of the RGB image light so that the visibility of the display image is improved. Can be improved.

<About hue difference>
Next, the above-described hue difference will be described using the LCh color system. FIG. 4A is a schematic explanatory diagram of the LCh color system, and FIG. 4B is an explanatory diagram showing a hue angle difference between image light and external light in the LCh color system. The LCh color system is a color system that expresses a color using lightness, saturation, and hue angle, and can express a difference between two colors by a difference in hue angle. The above-described dimming shutter 4 desirably has a characteristic that the saturation C of the transmitted light is 10 or more when light from a C light source that is one of the standard light sources is incident.

  Here, the C light source is one of the standard light sources defined by the International Commission on Illumination (CIE), which has a color temperature of 6774K (Kelvin) and is set close to average daylight. Point to. Dimming when light with small wavelength characteristics (light with very low saturation C in the LCh color system) such as white light and natural light typified by the C light source, which is one of the standard light sources, enters. Since the saturation C of the transmitted light is 10 or more by the shutter 4, the color of the external light transmitted through the light-reducing shutter 4 (reduced) can be reliably identified, and the color difference between the image light and the external light can be determined. The display performance (visibility) can be reliably improved.

  For example, when the dimming shutter 4 dimmes with the B wavelength range as the specific wavelength range, the center wavelength (peak wavelength) of the specific wavelength range is 480 nm, and the transmittance of the dimming shutter 4 at the wavelength 480 nm is 50%. If the wavelength width of the specific wavelength region is 60 nm, the saturation C is 29. Further, when the light-reducing shutter 4 is dimmed using the G wavelength region as a specific wavelength region, the central wavelength (peak wavelength) of the specific wavelength region is 540 nm, and the transmittance of the light-reducing shutter 4 at the wavelength 540 nm is 45%. If the wavelength width of the specific wavelength region is 80 nm, the saturation C is 28. Thus, if the saturation C is a value of 10 or more, the visibility of the video can be improved with certainty. By the way, when a shutter having no wavelength characteristic (the same transmittance in the entire wavelength region of visible light) is used as a dimming shutter, the saturation C when the transmittance of the shutter is 10%, 30%, and 50% is The values are 5.3, 7.6, and 9.0, respectively, which are very small values of less than 10, so that the visibility of the video cannot be improved.

  Further, for example, the image light incident on the optical pupil E is monochromatic green, the peak wavelength of the image light is 520 nm, the half width of the image light is 15 nm, and the external light incident on the optical pupil E is a specific wavelength of 480 to 560 nm. Let the light be dimmed. In FIG. 4B, when attention is paid to the hue difference between the image light and the external light, that is, the hue angle difference, the image light that is green corresponds to light having a hue angle of about 160 degrees, and the green region is reduced. The emitted external light corresponds to purple light having a hue angle of about 320 degrees. Therefore, if the hue angle difference between the image light and the external light is Δh, Δh = 160 degrees.

  The hue changes from red to red, orange, yellow, yellow-green, green, blue-green, blue, purple in order of 45 degrees counterclockwise, and the hue angle difference is 45 degrees or more and 315 degrees or less. The color difference can be fully recognized. In other words, the visibility of the video can be improved by the “hue difference”. Furthermore, when the hue angle difference is 135 degrees or more and 225 degrees or less, the colors are in a complementary color relationship, and visibility is most improved.

  That is, by satisfying 45 ° ≦ Δh ≦ 315 °, it can be said that the visibility of the display image is improved because the hue of the image light and that of the external light are different. Further, by further satisfying 135 ° ≦ Δh ≦ 225 °, it can be said that the visibility of the display image is further improved because the image light and the external light have a substantially complementary relationship.

  Even under the following conditions, the “hue difference” can be used to improve video visibility. For example, the image light incident on the optical pupil E is a single green color, the peak wavelength of the image light is 520 nm, and the half-value width of the image light is 15 nm. Then, the light reducing shutter 4 is composed of a liquid crystal element using a chiral nematic liquid crystal, which will be described later, and external light incident on the optical pupil E is light with a specific wavelength range of 490 to 570 nm reduced, and the center of the specific wavelength range The wavelength (peak wavelength) is set to 540 nm, the transmittance of the light reducing shutter 4 at the wavelength of 540 nm is set to 45%, the wavelength width of the specific wavelength range is set to 70 nm, and external light is used as a standard light source (C light source). In this case, the saturation C of the external light transmitted through the dimming shutter 4 is 28, and the hue angle h is 350 degrees. Further, the saturation C of the image light is 25, and the hue angle h is 157 degrees.

  That is, the saturation C of the external light transmitted through the light reducing shutter 4 is 28, which is sufficiently higher than 10, so that the external environment can be sufficiently recognized as a color different from the image. Further, the hue angle difference Δh between the image light and the external light is 350−157 = 193, and a substantially complementary relationship is obtained, so that the visibility of the display image can be sufficiently improved.

<About the dimming shutter configuration>
Next, a specific configuration of the dimming shutter 4 will be described. FIG. 5 is a cross-sectional view showing a configuration example of the light reducing shutter 4. The dimming shutter 4 can be composed of a liquid crystal element that can change the transmittance in a specific wavelength range to be dimmed. The liquid crystal element includes two transparent substrates 4a and 4a, transparent electrodes 4b and 4b disposed on the substrates 4a and 4a, and a liquid crystal layer 4c sandwiched between the substrates 4a and 4a via the electrodes 4b and 4b. And is configured. The substrates 4a and 4a may be made of glass, but it is more preferable that the substrates 4a and 4a are made of plastic from the viewpoint of safety, considering that the dimming shutter 4 is disposed in front of the eyes.

  By changing the alignment state of the liquid crystal molecules in the liquid crystal layer 4c by applying a voltage to the electrodes 4b and 4b, the transmittance can be varied only in a specific wavelength region as shown in FIG. Then, switching between two different states, a dimming state in which the transmittance in a specific wavelength region is reduced and a transmission state in which the transmittance in the specific wavelength region is increased to substantially match the transmittance in other wavelength regions Is possible. Thereby, when the image is not observed (when the image is not displayed on the display element 2), the external environment can be observed brightly and naturally without coloring by setting the light reducing shutter 4 to the transmission state. . On the other hand, at the time of video observation, the visibility of the video can be improved by setting the dimming shutter 4 to the dimming state as described above.

  Here, the light-reducing shutter 4 can be composed of a liquid crystal element using guest-host liquid crystal or chiral nematic liquid crystal as the liquid crystal layer 4c. Hereinafter, these liquid crystals will be described in detail.

[Guest host LCD]
The guest-host liquid crystal is, for example, a liquid crystal in which nematic liquid crystal molecules (hosts) are dissolved dichroic dyes (guests) having different light absorption characteristics in the major axis direction and the minor axis direction of the molecules. By changing the alignment state of the liquid crystal molecules by applying a voltage, the alignment direction of the guest molecules can be changed, and the transmittance of the liquid crystal layer can be changed by absorption of the guest molecules. If a liquid crystal exhibiting dichroism is used for the liquid crystal layer 4c itself, the same dimming shutter 4 can be produced using only the host without using a guest.

  Here, the color of the light transmitted through the guest-host liquid crystal by a white light source (for example, sunlight) is transparent because the guest molecules are aligned with the host liquid crystal in parallel with the major axis when the voltage is applied. Therefore, the light source light is white. On the other hand, when no voltage is applied, the refractive index differs because the long axis directions of the guest molecule and the host liquid crystal are not aligned, and light is absorbed by the dichroic dye, resulting in a color tone.

  For example, when a blue dichroic dye is used, the transmittance is the lowest in the vicinity of a red wavelength (for example, 640 nm) which is a substantially complementary color. Similarly, when a yellow dichroic dye is used, the transmittance is the lowest in the vicinity of a blue wavelength (for example, 460 nm) which is a substantially complementary color, and when an orange dichroic dye is used, The transmittance is the lowest in the vicinity of a green wavelength (for example, 520 nm) which is the substantially complementary color. That is, by selecting a dichroic dye according to the color of the image light to be used and reducing the transmittance in a specific wavelength region, it is possible to improve the visibility of the image light.

  As dichroic dyes, azo, anthraquinone, benzoquinone, naphthoquinone, polymethine, and tetrazine dyes are known. Among them, anthraquinone dyes have a high dichroic ratio, light resistance, solubility, etc. And is preferable. The blending amount of the dichroic dye is slightly different depending on the type of color to be used. For example, in the case of an orange or yellow dye, 0.5% to 2.0% by weight and 1% by weight of the liquid crystal component In the case of a blue dye, it is preferably 0.25 to 1.0% by weight, preferably 0.5% by weight.

  Thus, by selecting and adjusting the type and blending amount of the dichroic dye that is the guest molecule, it is possible to reduce the light by dropping the arbitrary wavelength region to the arbitrary transmittance. Further, the transmittance of the liquid crystal can be varied by applying a voltage, and the transmittance in a specific wavelength region can be varied.

[Chiral Nematic LCD]
The chiral nematic liquid crystal is a liquid crystal that exhibits a cholesteric liquid crystal phase at room temperature by adding a chiral material to the nematic liquid crystal. By using a chiral nematic liquid crystal, a planar state (selective reflection state) and a focal conic state (transparent state) can be switched by applying a voltage, and the transmittance of the liquid crystal can be made variable. Furthermore, even if the voltage application is stopped, the above two states can be stably maintained (because of the memory property), so that power is saved.

  Here, examples of the nematic liquid crystal include conventionally known liquid crystal ester compounds, liquid crystal pyrimidine compounds, liquid crystal cyanobiphenyl compounds, and liquid crystals having polar groups such as fluorine atoms, fluoroalkyl groups, and cyano groups. A single compound or a mixture of these can be used.

  On the other hand, as the chiral material to be added, for example, a cholesteric liquid crystal having a cholesteric ring, a chiral nematic liquid crystal, or an organic compound that does not exhibit liquid crystallinity but has a function of twisting nematic liquid crystal molecules can be used. For example, biphenyl compounds, terphenyl compounds, ester compounds, pyrimidine compounds, azoxy compounds, etc. that give nematic liquid crystal molecules a layered helical structure (a molecular structure in which liquid crystal molecules rotate 360 ° along the helical structure of liquid crystal molecules) Can be used. A commercially available chiral material having an optically active group at the terminal group of the compound can also be used, and a cholesteric liquid crystal having a cholesteric ring typified by cholesteric nonanolate can also be used.

  The chiral nematic liquid crystal can change the pitch of the spiral structure of the chiral nematic liquid crystal by changing the addition amount of the chiral dopant (chiral material) to the nematic liquid crystal, thereby changing the selective reflection wavelength region of the liquid crystal ( Control). For example, when MLC-6247 and R1011 (both manufactured by Merck & Co., Inc.) are contained as chiral materials in an amount of 8.91% by weight and 4.50% by weight, respectively, with respect to the total amount of the liquid crystal composition, light having a wavelength near 470 nm is emitted. It can be selectively reflected. Further, when MLC-6247 and R1011 (both manufactured by Merck) are contained as chiral materials in amounts of 4.20% by weight and 5.26% by weight, respectively, with respect to the total amount of the liquid crystal composition, light having a wavelength near 550 nm is emitted. It can be selectively reflected. Furthermore, when MLC-6247 and S1011 (both manufactured by Merck & Co., Inc.) are contained as chiral materials in an amount of 8.73 wt% and 2.36 wt%, respectively, with respect to the total amount of the liquid crystal composition, light having a wavelength near 660 nm is emitted. It can be selectively reflected.

  Thus, by adjusting the amount of chiral material added (for example, about 8 to 40% by weight), the wavelength region for selective reflection can be changed, and the light reducing shutter 4 can be used. However, the addition amount of the chiral material is desirably about 10 wt% to about 45 wt%, for example, based on the total weight of the nematic liquid crystal and the chiral material. When the amount of the chiral material added is 10% by weight or less, sufficient memory properties (that is, the retention of the colored state in the colored state after the voltage application is stopped, or the scattering state in the scattered state) This is because there is a case where the cholesteric phase is not exhibited or solidified at room temperature at 45% by weight or more. In addition, as for the addition amount of a chiral material, 15 to 40 weight% is more desirable.

(3. Other configurations of the video display device)
FIG. 7 is an explanatory diagram showing another configuration of the video display device 1. A plurality of the dimming shutters 4 may be provided so as to be selectively usable. However, it is assumed that the specific wavelength regions in which the respective light-reducing shutters 4 are dimmed are different from each other (there are no overlapping wavelength regions). Hereinafter, the light reducing shutter 4 that reduces the light with the wavelength region of R as the specific wavelength region is referred to as a light reducing shutter 4R. Further, the light-reducing shutter 4 that dims with the G wavelength range as the specific wavelength range is referred to as a light-reducing shutter 4G, and the light-reducing shutter 4 that is dimmed with the B wavelength range as the specific wavelength range as the light-reducing shutter 4B. .

  As shown in FIG. 7, a plurality of light-reducing shutters 4R, 4G, and 4B having different specific wavelength regions with low transmittance are arranged to overlap each other, and R (635 ± 10 nm), G (520 ± 10 nm) are used as the optical path combiner 3. , B (465 ± 10 nm) HOE that diffracts and reflects video light of each color is used. In this configuration, by selectively using any one of the dimming shutters 4R, 4G, and 4B, it becomes possible to improve the visibility corresponding to each color of the image light. That is, even when image light of one of RGB colors is generated by the display element 2 and can be guided to the optical pupil E through the optical path combiner 3, any one of the reductions depending on the color of the image light used. By reducing the transmittance of the optical shutter 4 in a specific wavelength region, it is possible to improve the visibility with respect to each image light having a different wavelength.

  Thus, by providing a plurality of light-reducing shutters 4R, 4G, and 4B, even if the color (single color) of the image light is switched, the light-reducing shutter 4 corresponding to the color of the image light is selected and used. Accordingly, it is possible to reduce external light corresponding to each color of the image light, and it is possible to improve the visibility corresponding to each color of the image light. Therefore, in the configuration in which a plurality of light-reducing shutters 4R, 4G, and 4B are provided, for example, LEDs that emit RGB light as light sources are used, and any one of RGB light is applied to the display element 2 so that the display element 2 This is very effective in a configuration in which monochromatic light is emitted as image light. Even if the image light is not a single color but a color, only a specific color may be dimmed according to the overall color tone of the image. For example, when an underwater image or the like in diving is displayed on the display element 2, the blue image occupies most of the display image as a whole. In such a case, it is possible to obtain a corresponding improvement in visibility only by dimming only the B light of the external light using the B light reducing shutter.

(4. Specific examples applied to HMD)
Next, a specific configuration when the video display device 1 described above is applied to an HMD will be described.

  FIG. 8 is a cross-sectional view showing a schematic configuration of the video display device 11 applied to the HMD. The video display device 11 allows the observer to observe the outside world through see-through, and displays a monochromatic image and provides it to the viewer as a virtual image. The video display device 11 (see FIG. 1 and the like) described above. It corresponds. The video display device 11 includes a video display unit 21, an eyepiece optical system 31, and a dimming shutter 41. The video display unit 21 includes a light source 22, a unidirectional diffuser plate 23, a condenser lens 24, and an LCD 25.

  The light source 22 is configured by an LED that emits green color light having a central wavelength of, for example, 520 nm. The unidirectional diffuser plate 23 diffuses illumination light from the light source 22, but the degree of diffusion differs depending on the direction. More specifically, the unidirectional diffuser plate 23 diffuses incident light in a direction perpendicular to the paper surface (horizontal direction) of FIG. 8 by about 40 ° and in a direction parallel to the paper surface (a direction perpendicular to the horizontal direction). Diffuses incident light by about 0.2 °. The condenser lens 24 is an illumination optical system that condenses the light diffused by the unidirectional diffuser plate 23. The condenser lens 24 is arranged so that the diffused light efficiently forms the optical pupil E. The LCD 25 is a display element that displays an image by modulating light from the light source 22 for each pixel based on a video signal, and is configured by a transmissive liquid crystal display element that does not include a color filter, for example. . The LCD 25 corresponds to the display element 2 (see FIG. 1 and the like) described above.

  On the other hand, the eyepiece optical system 31 guides the image light from the LCD 25 to the optical pupil E, and transmits the external light to the optical pupil E so that the external world is displayed together with the virtual image of the display image at the position of the optical pupil E. Let them see through. The eyepiece optical system 31 includes a cemented prism (a cemented optical member), and configures a telecentric optical system. Specifically, the eyepiece optical system 31 is formed by joining an eyepiece prism 32 and a deflection prism 33, which are optical members, with an optical path combiner 34 interposed therebetween.

  The eyepiece prism 32 and the deflection prism 33 are joined with an adhesive. The eyepiece prism 32 is formed in a shape in which the lower end portion of the parallel plate is wedge-shaped and the upper end portion is thickened, and guides the image light from the LCD 25 by totally reflecting it internally. The eyepiece prism 32 has surfaces 32a, 32b, and 32c. The surface 32a is an incident surface on which the image light from the image display unit 21 is incident, and the surfaces 32b and 32c are surfaces facing each other. Among these, the surface 32b is a total reflection surface and an emission surface.

  The deflection prism 33 is configured to be a substantially parallel flat plate integrated with the eyepiece prism 32 by forming the upper end portion of the parallel plate along the lower end portion of the eyepiece prism 32. When the deflecting prism 33 is not joined to the eyepiece prism 32, external light is refracted when passing through the wedge-shaped lower end portion of the eyepiece prism 32, so that the external field image observed through the eyepiece prism 32 is distorted. However, the deflection prism 33 is joined to the eyepiece prism 32 to form an integral substantially parallel plate, whereby the deflection when the external light passes through the wedge-shaped lower end of the eyepiece prism 32 is canceled by the deflection prism 33. Can do. As a result, it is possible to prevent distortion in the external image observed through the see-through.

  The optical path combiner 34 is a reflective optical element that reflects the image light from the LCD 25 guided inside the eyepiece prism 32 and guides it to the optical pupil E, and transmits external light to the optical pupil E, for example, a volume phase. It is composed of a type and reflection type HOE. This HOE diffracts light in a wavelength band of, for example, 520 ± 10 nm that is incident at a specific incident angle. The optical path combiner 34 is attached to the inclined surface at the lower end of the eyepiece prism 32, and as a result, is sandwiched between the eyepiece prism 32 and the deflection prism 33. By forming the HOE between the two transparent members (the eyepiece prism 32 and the deflection prism 33), the HOE does not come into contact with the outside air, so that the optical performance can be kept stable.

  The dimming shutter 41 is a dimming unit that reduces the transmittance of external light, and corresponds to the above-described dimming shutter 4 (see FIG. 1 and the like). Here, the dimming shutter 41 is composed of a liquid crystal element that varies the transmittance of light in a specific wavelength region of 480 to 560 nm by applying a voltage, and includes, for example, the above-described chiral nematic liquid crystal. The dimming shutter 41 is disposed on the side opposite to the optical pupil E with respect to the optical path combiner 34.

  In the above configuration, light (G light) emitted from the light source 22 of the video display unit 21 is diffused by the unidirectional diffusion plate 23, condensed by the condenser lens 24, and enters the LCD 25. The light incident on the LCD 25 is modulated for each pixel based on the video signal and is emitted as video light. At this time, a green image is displayed on the LCD 25.

  The image light from the LCD 25 enters the eyepiece prism 32 of the eyepiece optical system 31 from its upper end surface (surface 32a), is totally reflected a plurality of times by the two opposing surfaces 32b and 32c, and enters the optical path combiner 34. To do. The light incident on the optical path combiner 34 is diffracted and reflected there, is emitted through the surface 32b, and reaches the optical pupil E. Therefore, at the position of the optical pupil E, the observer can observe an enlarged virtual image of the image displayed on the LCD 25.

  On the other hand, the eyepiece prism 32, the deflecting prism 33, and the optical path combiner 34 transmit almost all the external light, so that the observer can observe the external world. Therefore, the virtual image of the image displayed on the LCD 25 is observed while overlapping a part of the outside world. From the above, it can be said that the optical path combiner 34 is a combiner that guides the image light and the external light simultaneously to the eyes of the observer.

  At this time, in a state where the light reducing shutter 41 does not reduce the transmittance, the observer can observe the outside world as usual through the light reducing shutter 41, the optical path combiner 34, and the like. On the other hand, in a state where the light reduction shutter 41 has reduced transmittance, light in the green wavelength range (specific wavelength range) including the wavelength range of green image light is reduced by the light reduction shutter 41 in the external light. Since the light is emitted, the external light incident on the optical pupil E is slightly colored in a purple hue which is a substantially complementary color of green. Accordingly, the visibility of the image light is sufficiently improved due to the hue difference between the purple of the external light and the green of the image light and the luminance difference due to the dimming of the external light.

  As described above, the dimming shutter 41 dimmes only in a specific wavelength region including the wavelength region of green image light in the visible light region, so that external light is bright. Furthermore, the visibility of the image can be improved not only by the luminance difference between the ambient light and the image light, but also by the hue difference between the ambient light and the image light. Even if it is not so large, the visibility can be sufficiently improved. That is, even when the external light is bright and the external light is relatively little colored, high image visibility can be sufficiently obtained.

  Further, the eyepiece optical system 31 includes an optical path combiner 34 composed of a volume phase type reflection type HOE. Volume phase type reflection type HOE has high diffraction efficiency, and the half-value wavelength width of the diffraction efficiency peak is narrow. Therefore, a bright image can be observed by using such a HOE and adopting a configuration in which the image light from the LCD 25 is diffracted and reflected by the HOE and guided to the optical pupil E. In addition, since the transmittance of external light is increased, a bright external environment can be observed.

  In addition, since the image light is guided using total reflection in the eyepiece prism 32, the thickness can be reduced to the same level as that of a normal spectacle lens (for example, about 3 mm), and the eyepiece prism 32 can be made compact. While being able to be lightweight, the transmittance of external light becomes high and the external environment can be observed well. Further, the LCD 25 can be disposed on one end side of the eyepiece optical system 31, that is, in the vicinity of the visual field, and a wide external field viewing angle can be ensured.

  The HOE has an axially asymmetric positive optical power for enlarging an image displayed on the LCD 25 and constitutes at least a part of the eyepiece optical system 31. Therefore, the eyepiece optical system 31 can be reduced in size. While configuring, it is possible to increase the degree of freedom of arrangement of each optical member constituting the apparatus, to reduce the size and weight of the apparatus, and to observe an image with good aberration correction.

  Further, as described above, the optical path combiner 34 is composed of a volume phase type reflection type HOE that diffracts only light having a specific wavelength at a specific incident angle. The external light transmitted through the prism 33 and the optical path combiner 34 is not affected. Therefore, in a state where the light reduction shutter 41 does not reduce the transmittance, the observer observes the virtual image of the display image on the LCD 25 through the optical path combiner 34, and the eyepiece prism 32, the deflection prism 33, and the optical path combiner 34. It is possible to observe the outside world as usual and clearly.

  In the above description, an example in which the light source 22 emits G light and the dimming shutter 41 attenuates using the G wavelength region as a specific wavelength region has been described. However, when the light source 22 emits R light or B light. The dimming shutter 41 may be configured so as to be dimmed with the wavelength region of R or the wavelength region of B as a specific wavelength region.

  Next, an HMD to which the video display device 11 is applied will be described. FIGS. 9A, 9B, and 9C are a plan view, a front view, and a side view showing a schematic configuration of the HMD, respectively. The HMD includes the above-described video display device 11 and support means 12 that supports the video display device 11, and as a whole looks like one lens (for example, for the left eye) is removed from general glasses. Yes. In the video display device 11, a portion corresponding to the right eye lens of the glasses is configured by bonding the eyepiece prism 32 and the deflection prism 33.

  The dimming shutter 41 of the video display device 11 is located in front of both eyes of the observer and is formed in a shape that reduces both the transmittances of external light incident on both eyes, but the video display device 11 is disposed. It may be arranged only in front of one eye on the one side so as to reduce the transmittance of external light incident on one eye.

  The support unit 12 supports the video display device 11 in front of the observer's eyes (for example, in front of the right eye), and includes a bridge 13, a frame 14, a temple 15, a nose pad 16, and a cable 17. is doing. The frame 14, the temple 15 and the nose pad 16 are provided as a pair on the left and right sides. However, when these are distinguished from each other, the right frame 14R, the left frame 14L, the right temple 15R, the left temple 15L and the right nose pad 16R. The left nose pad 16L is expressed.

  One end of the video display device 11 is supported by the bridge 13. In addition to the video display device 11, the bridge 13 supports the left frame 14 </ b> L, the nose pad 16, and the dimming shutter 41. The left frame 14L supports the left temple 15L so as to be rotatable. On the other hand, the other end of the video display device 11 is supported by the right frame 14R. An end of the right frame 14R opposite to the support side of the video display device 11 supports the right temple 15R so as to be rotatable. The cable 17 is a wiring for supplying an external signal (for example, a video signal, a control signal) and power to the video display device 11, and is provided along the right frame 14R and the right temple 15R.

  When the observer uses the HMD, the right temple 15R and the left temple 15L are brought into contact with the right and left heads of the observer, and the nose pad 16 is placed on the nose of the observer so as to wear general glasses. The HMD is attached to the observer's head. When an image is displayed on the image display device 11 in this state, the observer can observe the image on the image display device 11 as a virtual image and can observe the outside world through the image display device 11 in a see-through manner. it can.

  As described above, since the video display device 11 is supported by the support means 12, the observer can observe the video provided from the video display device 11 in a hands-free manner. In addition, since the observation direction of the observer is determined in one direction, there is an advantage that the observer can easily search for a display image even in a dark environment.

  The HMD may have a configuration in which two video display devices 11 are arranged in front of both eyes of the observer. In this case, the above-described dimming shutter 41 may be positioned in front of both eyes of the observer and reduce both the transmittance of external light incident on both eyes.

(5. Supplement)
Of course, it is possible to appropriately combine the configurations described in the present embodiment to configure the video display device and thus the HMD. For example, it is of course possible to apply the configuration of FIG. 7 provided with a plurality of light reducing shutters 4 to the video display device 11 of FIG.

  The video display device described in the present embodiment can also be applied to, for example, a head-up display (HUD).

  The present invention is applicable to HMD and HUD.

It is explanatory drawing which shows typically the structure of the video display apparatus of this invention. (A) is explanatory drawing which shows the wavelength characteristic of the transmittance | permeability of the light reduction shutter of the said video display apparatus, (b) is explanatory drawing which shows the wavelength characteristic of external light, (c) is an optical pupil. It is explanatory drawing which shows the wavelength characteristic of the image light and external light which inject into A. (A) is explanatory drawing which shows typically the optical path of the image light which is diffracted and reflected by the optical path combiner in the said video display apparatus, and injects into the center and upper-lower end of an optical pupil, (b) is the said optical path combiner. It is explanatory drawing which shows the wavelength characteristic of the diffraction efficiency of HOE which comprises. (A) is typical explanatory drawing of LCh color system, (b) is explanatory drawing which shows the hue angle difference of the image light and external light in a LCh color system. It is sectional drawing which shows one structural example of the said light reduction shutter. It is explanatory drawing which shows the change characteristic of the transmittance | permeability of the said light reduction shutter. It is explanatory drawing which shows the other structure of a video display apparatus. It is sectional drawing which shows the structure of the outline of the video display apparatus applied to HMD. (A) (b) (c) is the top view, front view, and side view which respectively show the structure of the outline of the said HMD. It is explanatory drawing which shows typically the optical path of the image light and external light which inject into an optical pupil with a fixed magnitude | size.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image display apparatus 2 Display element 3 Optical path combiner 4 Dimming shutter (dimming means)
4R dimming shutter (dimming means)
4G dimming shutter (dimming means)
4B dimming shutter (dimming means)
4c Liquid crystal layer (guest host liquid crystal, chiral nematic liquid crystal)
DESCRIPTION OF SYMBOLS 11 Image display apparatus 12 Support means 25 LCD (display element)
31 Eyepiece optical system 32 Eyepiece prism (optical member)
34 Optical path combiner (hologram optical element)
E Optical pupil

Claims (14)

A display element for displaying an image;
An image that reflects the image light from the display element and guides it to the optical pupil, and transmits an external light to the optical pupil to guide it to the optical pupil. A display device,
The light path combiner is disposed on the opposite side of the optical pupil, and further comprises a dimming means for reducing the transmittance of external light,
The dimming means is characterized in that, in the visible light region, the transmittance in a specific wavelength region including the same wavelength region as the image light incident on the optical pupil is lowered than the transmittance in a wavelength region other than the specific wavelength region. A video display device. When external light transmittance in the dimming means a wavelength width becomes an intermediate value between the maximum value and the minimum value is set to W _1, the half-value wavelength width of the maximum intensity of the image light entering the optical pupil and W _2,
W ₂ <W ₁ ≦ 100 nm
The video display device according to claim 1, wherein: The optical path combiner is a volume phase type reflection type hologram optical element,
The diffraction reflection wavelength range of the hologram optical element is included in the specific wavelength range,
When the half-value wavelength width of the diffraction efficiency of the hologram optical element is W ₃ ,
3W ₃ ≦ W ₁
The video display device according to claim 2, wherein:   The video display device according to claim 1, wherein the specific wavelength range is one of red, green, and blue.   5. The image according to claim 1, wherein the dimming means has a saturation of transmitted light of 10 or more when light from a C light source which is one of standard light sources is incident. Display device. If the hue angle difference in the LCh color system between the external light incident on the optical pupil and the image light incident on the optical pupil is Δh,
45 ° ≦ Δh ≦ 315 °
The video display device according to claim 5, wherein: 135 ° ≦ Δh ≦ 225 °
The video display device according to claim 6, wherein:   The video display device according to claim 1, wherein the transmittance of the specific wavelength region in the dimming means is variable.   9. The video display device according to claim 8, wherein the dimming means is a liquid crystal element using guest-host liquid crystal.   9. The image display device according to claim 8, wherein the dimming means is a liquid crystal element using chiral nematic liquid crystal. A plurality of the dimming means are provided so as to be selectively usable.
The video display device according to claim 1, wherein the specific wavelength ranges of the dimming units are different from each other. It further has an optical member that guides the image light from the display element by totally reflecting it inside,
The optical path combiner is a volume phase type reflection type hologram optical element,
12. The image display device according to claim 1, wherein the hologram optical element guides the image light from the display element guided through the optical member to the optical pupil by diffracting and reflecting the image light. .   The hologram optical element has a positive optical power that is axisymmetric and constitutes at least a part of an eyepiece optical system that guides image light from the display element to an optical pupil. 12. The video display device according to 12. A video display device according to any one of claims 1 to 13,
A head-mounted display comprising: support means for supporting the video display device in front of an observer's eyes.

Images